Objectives: To determine whether the use of the new macrolides (azithromycin, clarithromycin, roxithromycin) during the first trimester of pregnancy is associated with an increased risk of major malformations.
Study design: In a prospective multi-center study, pregnancy outcome was compared between pregnant women exposed to one of the new macrolides during the first trimester of pregnancy and two comparison groups one exposed to other antibiotics and the other to other non-teratogenic medications. All women enrolled in the study called one of the three participating teratogen information services (TIS). Group 1 macrolides (n=161), group 2 other antibiotics (n=213) and group 3 non-teratogens (n=740).
Results: A total of 161 women exposed to the new macrolides (118 were exposed in the first trimester of pregnancy) and 953 from a comparison groups were followed up. The rate of major malformations in the study group was 4.1% compared to 2.1% in the other antibiotics exposed group (OR=1.41, 95% CI 0.47-4.23) and 3.0% in the non-teratogens exposed group. The rate of elective terminations of pregnancy was significantly higher in the exposed group in compare to both comparison groups.
Conclusion: Our study, although relatively small sized, suggests that the use of the new macrolides during the first trimester of pregnancy does not represent an increased risk for congenital malformations strong enough for an induced abortion after such an exposure. Elective terminations of pregnancy because of early exposure to these medications should be reconsidered.